The present invention relates to seed planting assemblies in general, and in particular relates to a method and apparatus for maintaining seed trench depth during operation of a seed planting assembly.
Seed planting units generally include a laterally extending tool bar that supports a plurality of parallel planting units (also known as row units). The tool bar is typically coupled to a tractor or like vehicle suitable for towing the planting assembly along a field that is to be seeded to a crop. Each planting unit includes a device for opening a seed trench in the ground as the tractor draws the tool bar across a field to be seeded.
Each planting unit further includes a seed meter to dispense seeds at a controlled rate into a seed trench as the meter is advanced above and along the seed trench during operation. Generally, seeds are delivered to the metering assembly from a seed hopper located on the planting unit or, alternatively, from a smaller container fed from a centralized large hopper used to feed all or a portion of the planting units. Each planting unit further includes a closing assembly that moves soil at the sides of the seed trench to close the seed trench over the planted seeds. Adjacent planting units are laterally spaced a sufficient distance to form seed trenches that are spaced a corresponding distance apart that is suitable for the type of seed being planted.
Typically a pair of gauge wheels are disposed adjacent the outer surfaces of the seed trench-opening device. The height of the gauge wheels relative to the seed trench-opening device generally is set by the user, which thereby predetermines the depth of the seed trench. However, when one of the gauge wheels travels over an obstacle that is elevated with respect to the soil, such as a rock, hard lump of dirt, heavy residue, and the like, the planting unit will rise, thereby decreasing the seed trench depth. If the planting unit is traveling at a sufficient speed, the planting unit may become momentarily airborne, thereby further lifting the seed trench-opening device out of the ground.
It should be appreciated that a crop yield is maximized when all seeds emerge from the soil within a given timeframe relative to each other. Otherwise, if some seeds emerge later than others in a given row, the yield for that row can be substantially reduced. One known method for encouraging uniform seed emergence is to maintain the seed trench a constant depth when performing seed planting operations. Some planting units include a bracket that links the pair of gauge wheels. Accordingly, when one gauge wheel travels over an obstacle, the opposing gauge wheel to lower and maintain contact with the soil, thereby decreasing the seed trench depth by a distance equal to one-half the height of the obstacle. Conversely, when one of the gauge wheels travels over a depression, the opposing gauge wheel is raised an equal distance, thereby increasing the seed trench depth by a distance equal to one-half the depth of the depression. Such a system is described in U.S. Pat. No. 4,423,788.
While the above system has proved suitable for its intended purpose, it would be desirable to provide a method and apparatus for further reducing the change in seed trench depth when traveling over an obstacle or in a depression while performing seed planting operations.